Many articles, e.g., boats, airplanes, skis, air foils, mixing blades, have fluids flow over their surface. Such fluids include air, other gases, liquids, and semi-solids. The roughness of the surface of the article is critical, because it directly affects how efficiently the fluid flows over the article. The more efficiently a fluid flows, the less energy is required to transport it.
European Patent Application 354,022, published Feb. 7, 1990, discloses a method to increase the efficiency of fluid flow over a surface by attaching a flexible and/or stretchable substrate to the surface to reduce the drag resistance or increase the efficiency of a fluid flowing thereover. This substrate has small individual sections each of which has a patterned surface.
Another method of treating the surface of an article involves bringing an abrasive product into frictional contact with the surface such that a portion of the surface is abraded away. Abrasive products suitable for this purpose include coated abrasives, lapping abrasives, bonded abrasives, and non-woven abrasives. Such a manner of abrading, known as form grinding, is a standard procedure in the abrasives industry (see U.S. Pat. No. 3,794,474 and Kenneth B. Lewis and William F. Schleicher, The Grinding Wheel, Third Edition, Grinding Wheel Institute (1976), Chapter 14, pp. 165-176). In form grinding, a bonded abrasive wheel in which a form or shape is imparted to the outer periphery of the wheel is brought into contact with a workpiece, and the inverse of the shape of the bonded wheel is imparted to the surface of the workpiece.
U.S. Pat. No. 2,682,733 discloses an abrasive product comprising a fibrous backing having an abrasive coating thereon. The abrasive coating contains abrasive particles embedded in a binder. When the binder is uncured, the abrasive coating is subjected to a pressure die containing a plurality of ridges, which forms rectangular grooves running in two different directions. U.S. Pat. No. 4,773,920 discloses an abrasive product, i.e., a lapping film, having an abrasive composite formed of abrasive grains distributed throughout a radiation curable binder. The patent also discloses that a pattern can be imparted to the abrasive product by means of a rotogravure roll.
The foregoing references, however, do not teach an efficient method for treating the surface of a workpiece such that the surface will be provided with the type of profile that promotes efficient flow of fluids over it.